A federal judge on Monday denied Myriad’s request for a preliminary injunction that would have immediately stopped a rival company, Ambry Genetics, from offering a similar test.

Myriad’s lucrative monopoly on testing for mutations in two genes linked to breast cancer risk was shattered last June by the Supreme Court’s ruling that genes were not eligible for patents because they were products of nature.

Several laboratory companies, including Ambry, quickly began offering tests, in most cases undercutting the $4,000 Myriad charged for a full analysis of the two genes, which are known as BRCA1 and BRCA2. Ambry announced a price of $2,200.

But Judge Robert J. Shelby of the United States District Court in Salt Lake City said in an opinion on Monday that Ambry had raised “substantial questions” concerning whether those remaining claims were eligible for patents. He said therefore that Myriad had not established that it was likely to succeed in the case on the merits of its arguments, which is a legal requirement to win a preliminary injunction.

The upshot is that Ambry can continue to offer its test pending the outcome of a trial or a settlement, said Dr. Robert M. Cook-Deegan, a research professor at Duke University who has closely followed the case and the issue of gene patents.

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Charles Dunlop, chief executive of Ambry, called the ruling “a victory for the entire genetics community.” He said in a statement that Myriad’s lawsuit, after last year’s Supreme Court decision, “was a blatant attempt to maintain a monopoly state. We idealistically stood by our convictions throughout this process and are exhilarated by today’s ruling.”

Ronald Rogers, a spokesman for Myriad, said Myriad looked forward to presenting its case in court. Monday’s ruling, he said in an email, “is a denial of the preliminary injunction only” and “isn’t a ruling on the underlying merits of the case.”

Myriad has not sought preliminary injunctions against GeneDx, Invitae, Quest Diagnostics and Laboratory Corporation of America Holdings, which have also started offering tests for BRCA1 and BRCA2. It probably cannot do so now because Judge Shelby is also handing those cases.

The patent claims asserted by Myriad against Ambry included those for primers, which are little pieces of DNA used to amplify genes, and methods for analyzing the BRCA sequences.

Judge Shelby, in his 106-page opinion, agreed with Myriad’s contention that it would be harmed without the injunction because its ability to maintain the price of its test would be undermined. Medicare has already proposed cutting the reimbursement for Myriad’s test roughly in half.

Myriad is joined in the suit by some other organizations that share in the patent rights, including the University of Utah and the University of Pennsylvania.

A version of this article appears in print on March 11, 2014, on Page B3 of the New York edition with the headline: Patentholder on Breast Cancer Tests Denied Injunction in Lawsuit. Order Reprints|Today's Paper|Subscribe